A variety of analytical instruments can be used for analyzing analytes such as organic molecules. More recently, mass spectrometry has gained prominence because of its ability to handle a wide variety of analytes with high sensitivity and rapid throughput. A variety of ion sources have been developed for use in mass spectrometry, and many of these ion sources comprise an ionization chamber. During operation, an analyte is introduced into the ionization chamber through some type of mechanism for sample introduction. Once the analyte is positioned within the ionization chamber, ions are produced from the analyte in accordance with an ionization process. Examples of ionization processes comprise electron impact ionization, chemical ionization, plasma bombardment ionization, fast ion or atom bombardment ionization, field desorption ionization, laser desorption ionization, plasma desorption ionization, thermospray ionization, electrospray ionization, and the like.
Characteristics of ions that are produced using an existing ionization chamber can depend upon characteristics of certain surfaces of the ionization chamber. In particular, inner surfaces of the ionization chamber are typically exposed to an analyte during operation of the ionization chamber, and interaction of the inner surfaces with the analyte can produce a number of undesired effects, such as reduced sensitivity, reduced accuracy, lack of reproducibility, and the like. For example, if a portion of the analyte adheres to or becomes adsorbed on the inner surfaces, that portion of the analyte is often not effectively ionized, thus reducing sensitivity of mass spectrometric analysis. Also, interaction of the inner surfaces with the analyte can sometimes cause the analyte to degrade, such as by converting into different types of organic molecules or other reaction products. Depending upon the particular analyte, a variety of unexpected ions can be produced as a result of such degradation, thus adversely impacting sensitivity as well as accuracy and reproducibility of mass spectrometric analysis.
Degradation of inner surfaces of an existing ionization chamber can also adversely impact mass spectrometric analysis. In particular, degradation of the inner surfaces during operation of the ionization chamber can introduce undesirable chemical background noise in the resulting mass spectrum. Contamination of the inner surfaces with residual analytes or reaction products from previous tests can also introduce undesirable chemical background noise in the resulting mass spectrum. Thus, proper cleaning of the inner surfaces can be important for mass spectrometric analysis, particularly for analytes that are present in low concentrations as is the case for pesticide residues, drug residues, metabolites, and the like. However, certain cleaning processes can be abrasive and can cause the inner surfaces to degrade, thus adversely impacting mass spectrometric analysis as described above.